Questions tagged [radio-frequency]

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What is the most accurate instrument which can be used to measure frequency of radio waves without measuring wavelength and how accurate is it?

I wanted to know if there's an instrument that accurately measures the frequency of radio waves as I'm working on something and I didn't get anything good on web.
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2answers
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X-rays are absorbed by bone. If the width of the bone increased in proportion to the wavelength, would bone absorb radio waves?

What I’m interested in here, are the properties of different electromagnetic waves, and the factors that cause them to be absorbed by different materials and be influenced in other ways by different ...
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What causes the sudden change in atmospheric reflection of long-band radio waves?

This picture shows up a lot. The explanations that tend to accompany it say that the long-band radio waves above ~10m are reflected, whereas other wavelengths are scattered or absorbed or transmitted. ...
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is room temperature quantum (qubit) nuclear magnetic resonance possible?

I know it is possible to do room temperature NMR. Not just that but one can also use the earth's magnetic field for the nuclei to precess about. If done this way, one gets precession at about the KHz ...
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How does the human body affect radio reception?

My sister asked me why her small radio sometimes has better reception when she places her hand nearby (without touching) the antenna. I did some research and wanted to ask a few questions. Here are ...
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Lens Design 60GHz Radar

I'm trying to design a lens for a 60GHz radar chip however rather than focusing the radar beam I'd like to widen it to a specific width. Also, the radar antenna has a main beam width that is larger ...
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S Parameters in HFSS

I'm new to HFSS Software and I'm trying to plot Scattering parameters in HFSS for a dielectric resonator excited by a probe (shown in image). I know that the top cylinder has a higher dielectric than ...
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3answers
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How are phased arrays compatible with the photon concept?

Not a physicist (although I know how to develop and simulate phase arrays). Phased arrays are e.g. emitters sending waves with individual elements with a different phase so that they act ...
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Extreme Redshift Detection

There is a new paper in arXiv postulating that black holes might actually let some let some light out. This of course is very theoretical, but it postulates that the light would be redshifted to 640 ...
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1answer
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How do the arc and the straight line have equal length in this figure?

I have the following derivation in one of my physics problem related to range of a transmitting antenna: How is the distance QT equal to the length of arc PT? Can someone provide a quick explanation ...
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2answers
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Why do artificial transmissions of coherent EM waves tend to be isotropic at radio frequencies but directional at visible frequencies?

This is a somewhat soft question, and I'm far from an expert on the subject, so it's possible that my premise is factually incorrect. The practical generation mechanisms for useful real-world coherent ...
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Minimum detectable signal of base station in free space

I am studying for tomorrow's exam (Communication Systems, part of Computer Science course), and I've run into this question which involves some radio propagation physics. That's why I decided to post ...
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Doubt in radar question

This is a question(2.25) from introduction to radar systems by Merrill Skolnik 3rd edition. Plot the single-scan probability of detection as function of range, assuming a constant cross-section target ...
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Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
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Is there a frequency converting amplifier? [closed]

Frequency conversion means output of the amplifier is at a frequency different from that of the input.
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36 views

What are odd radio circles (ORCs) in Space?

There is a video (https://www.youtube.com/watch?v=jXnXbMcI8Lo&t=595s) about pure radio waves radiating in circles in space. Odd radio circles (ORCs) are not radiating any other wave length (...
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How to simply explain correlation between Range, Power and Bandwidth in RF Technologies?

First off, I don't have a great understanding about the physics behind radio frequency technologies. I'm working on a paper evaluating if LoRa infrastructure can help developing communities for a ...
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41 views

Complex reflection coefficient for a radio frequency wave

With an RF transmitter at location $P_1$ and a receiver at $P_2$, I would like to calculate how much power reaches $P_2$ via a reflection at a point $P_3$. Hence I need to know the reflection ...
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1answer
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Proxima Centauri radio signal

I have recently seen an article about an unusual radio signal coming from Proxima Centauri region. I understand there is a debate around the nature of this signal. My question is related to this ...
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1answer
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How does UWB enable much higher positioning accuracies than Narrowband

literature and internet articles often only explain UWB’s much higher positioning accuracies with its much higher bandwidth compared to the bandwidth of other narrowband technologies such as WiFi/...
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Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
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How does oxygen react to radio waves at 60Ghz?

Since there are 3 states of oxygen: 3Σ−g: The ground triplet state 1Δg: The ground singlet state 1Σ+g: An excited singlet state. What happens to the ground triplet state when it is exposed to the 60 ...
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How to compute the signal propagation loss from each position in a map to one particular receiver location?

I have read up on signal propagation models and RF simulation software. Most software I found computes the path loss for a transmitter at a particular position to each position in the map. I now want ...
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Klystron beam current versus cavity wall current

is there any way to estimate (because it cannot be directly measured) the RF cavity wall current in a Klystron output cavity? It is related to the electron beam current and I have even seen a formula ...
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Frequency modulation with a certain bandwidth

I came across this sentence in this paper. Alternatively, we modulate the frequency of the microwave excitation voltage at 971 Hz with a square wave and a bandwidth of 32MHz. In my limited FM ...
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1answer
139 views

Modulation Index of an AM wave

I have been given a question as RMS value of an RF(Radio Frequency) voltage after amplitude modulation to a depth of $50$% by a sinusoidal voltage is $80$ Volts. Calculate the RMS value of modulated ...
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How does Tx Power affect the Free Space Path Loss model?

On this website one can use the FSPL model to calculate the Path Loss. This is typically interpreted online as the theoretical signal strength (in dB) that one may receive (e.g. from some WiFi). ...
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How much does the sun emits in the radio spectrum, compared to artificial (human) emissions?

I would like to compare natural vs artificial (human) emissions in the radio spectrum (f < 1 THz). The goal is to bring some scientific facts in the debate for deployment of 5G. It's easy to find ...
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50 views

In what media the speed of light is slower than the speed of radio waves, if any?

In what media the speed of visible light is slower than the speed of radio waves, if any? Particles can be faster than visible light, but other electromagnetic waves?
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S-matrix for 2-port network

Consider an impedance $Z$ on a waveguide of impedance $Z_0$. I add a load $Z_L$ at the end of the line but I don't think it should enter in the calculation ? I call $1$ the left port, $2$ the right ...
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Surface Roughness of a material in CST

I am adding an aluminium with a rough surface in CST Studio, but there is only thickness input (how thick the rough surface is), but as per ISO standards they are different types of rough surface with ...
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Ferrite material in CST Studio

I want to add a ferrite material in CST Studio for shielding effectiveness simulations, but not able to find any dispersion data for the material. I want to add a ferrite material in CST Studio for ...
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1answer
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Will a sheet of carbon atoms reflect radio waves?

I am working out some details in a SciFi novel. I'm thinking of having spec ops who would use a device that could manipulate carbon atoms to form and maintain large, rigid, one-atom thick carbon ...
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1answer
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How I simulate this in CST Studio? [closed]

I am trying to simulate this coaxial transmission line setup for EMI shielding. Placed the Aluminium sample as seen below (in the middle). I am new on this software, learned simulating the coaxial ...
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Intuitive explanation of Nyquist rate?

Is there an intuitive way to understand Nyquist rate (i.e., that, in order to prevent loss, an analog signal must be digitized at a rate twice as high as the highest frequency component of the signal)....
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How to calculate resolution given sampling rate/size?

In a research paper documenting the analog to digital conversion process of an experiment’s radio receiver, the following is written: The station consists of 10 channels. Each channel writes 1 ...
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Inferring angle of source?

Given the relative distance of 3 radio antennae, I want to infer an incident angle for some radio source seen by all 3 antennae, which I know to be on the ground. All I know is the relative locations ...
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1answer
40 views

What does it take to build an effective Faraday cage at bedroom-scale? [closed]

I want to block all EMF transmissions -- tv, radio, cell phone, wifi etcetera. I'm not trying to protect myself from an atmospheric detonation or solar storms, just the RF / EM "noise" of ...
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Monotonicity of sum of two Fresnel Integrals

This question is cross posted on Math Stack Exchange https://math.stackexchange.com/questions/3747009/monotonicity-of-sum-of-two-fresnel-integrals I am studying single-knife edge diffraction of radio ...
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1answer
123 views

Why is the transmission data rate between Mars and Earth so low?

I read that we get between 500 and 32k bits per second when sending data from Mars to Earth. Apparently it's substantially higher between Moon and Earth. What are the reasons? Please explain the ...
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1answer
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What is “spectral turnover”?

In a paper which deals with the spectra of radio frequency cosmic events, the word “spectral turnover” is used. What is “spectral turnover”?
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Estimation of power of received radio signal

I would like to estimate the magnitude of a radio signal received from a transmitter by first principles: Transmitter antenna length $L=1$ m Transmitter antenna cross-sectional area $A=1\hbox{ cm}^2$ ...
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How can I calculate “temporal parallax”?

A radio transient was observed by an observatory. I know the observatory’s location, the pointing center of the beam in galactic coordinates and right ascension/declination, and the exact time the ...
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What is the “single pulse radiometer equation”?

This document https://arxiv.org/pdf/1601.03547.pdf refers to the “single pulse radiometer equation”. Apparently, it’s used to calculate the flux of radio transients. What is the “single pulse ...
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Is there a way to measure flux indirectly?

Is it possible to calculate the flux of some electromagnetic radiation (say, a radio wave) using other parameters?
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Do the free electrons causing the dispersion in the 'Dispersion Measure' of an FRB refract or re-emit the long-wavelength RF waves?

If the free electrons in the interstellar and intergalactic medium absorb then elastically re-emit the longer-wavelength radio waves coming from an FRB, that would reduce their power, because they are ...
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Why are low-frequency radio transients so rare?

Why are low-frequency radio transient (fast radio bursts, etc) so rare? Is it due to our observational equipment, or something intrinsic to transient phenomena?
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How is the “intensity” of a fast radio burst measured?

I’ve read that Fast Radio Bursts are very “intense”, but how is intensity measured?
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Can I calculate frequency limits using bandwidth and center frequency?

I’m given the centre frequency and bandwidth of a radio transient. I need to determine the frequencies over which the transient occurred. I know there’s a relationship between the two, but I’ve ...
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What’s the difference between FoV and IFoV?

I read that radio telescopes have “huge fields of view (FoV)”, but are unable to precisely localized objects due to their “small instantaneous field of view (IFoV)”. Apparently, somehow the size of ...

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